Method, system, and apparatus for diagnosing an exhaust aftertreatment component
According to one embodiment, an apparatus is disclosed for diagnosing a condition of a component of an exhaust aftertreatment system in exhaust receiving communication with an internal combustion engine where the exhaust aftertreatment system includes a selective catalytic reduction (SCR) catalyst. The diagnostic module is configured to determine a normalized tailpipe nitrogen-oxide NO x value based on a tailpipe NO x sensor signal and a ratio of an SCR inlet ammonia (NH 3 ) flow rate to an SCR inlet NO x flow rate. The apparatus also includes a component condition module configured to determine a condition of the component based on the normalized tailpipe NO x value.
1. An apparatus for diagnosing a condition of a component of an exhaust aftertreatment system in exhaust receiving communication with an internal combustion engine, the exhaust aftertreatment system having a selective catalytic reduction (SCR) catalyst, comprising:
a controller structured to be coupled to the exhaust aftertreatment system, the controller including:
a diagnostic module structured to determine a normalized tailpipe nitrogen-oxide NO x value based on a tailpipe NO x sensor signal and a ratio of an SCR inlet ammonia (NH 3 ) flow rate to an SCR inlet NO x flow rate;
a component condition module structured to determine a condition of the component based on the normalized tailpipe NO x value; and
an on-board diagnostic module structured to communicate an alert signal to an on-board diagnostic system, wherein the alert signal causes the on-board diagnostic system to provide an indication of the condition of the component to a user.
2. The apparatus of claim 1 , wherein the component comprises a hydrocarbon oxidation catalyst.
3. The apparatus of claim 1 , wherein the component comprises a particulate matter filter.
4. The apparatus of claim 1 , wherein the diagnostic module is structured to determine the normalized tailpipe NO x value only during transient engine operating conditions.
5. The apparatus of claim 4 , wherein the transient engine operating conditions comprise an engine outlet NO x flux being between upper and lower engine outlet NO x flux thresholds.
6. The apparatus of claim 1 , wherein the diagnostic module is structured to determine the normalized tailpipe NO x value only if a temperature condition of the SCR catalyst is within a predetermined temperature range.
7. The apparatus of claim 6 , wherein the temperature condition comprises a sum of an SCR mid-bed temperature weighted according to a first factor and an SCR outlet exhaust temperature weighted according to a second factor.
8. The apparatus of claim 1 , wherein the controller further includes a filtering module structured to convert the normalized tailpipe NO x value into an exponentially weighted moving average of the normalized tailpipe NO x value, and wherein the condition of the component is based on the exponentially weighted moving average of the normalized tailpipe NO x value.
9. The apparatus of claim 1 , wherein the component condition module determines the condition of the component based on a hysteresis of a plurality of normalized tailpipe NO x values.
10. The apparatus of claim 1 , wherein the diagnostic module is structured to determine the normalized tailpipe NO x value only when enablement conditions are met, the enablement conditions comprising a temperature condition of the SCR catalyst being within a predetermined temperature range, transient engine operating conditions, the tailpipe NO x sensor signal is within a first predetermined range, an NH 3 -to-NO x ratio entering the SCR catalyst is within a second predetermined range, there is no active component regeneration occurring, and the NO x sensor signal is currently stable.
11. The apparatus of claim 10 , wherein the enablement conditions further comprise a rate of change of switching between ammonia reductant modes is within a predetermined range, excess hydrocarbons are not entering into the component of the exhaust aftertreatment system, the NO x sensor signal historically has been stable, and no on-board diagnostic faults are triggered.
12. A system, comprising:
an internal combustion engine generating an exhaust gas;
an exhaust aftertreatment system in exhaust gas receiving communication with the internal combustion engine, the exhaust aftertreatment system comprising an exhaust treatment component and a selective catalytic reduction (SCR) catalyst downstream of the exhaust treatment component; and
a controller structured to determine a normalized level of nitrogen-oxide (NO x ) in exhaust gas downstream of the SCR catalyst, and further structured to determine a condition of the exhaust treatment component based on the normalized level of NO x , and further structured to communicate an alert signal to an on-board diagnostic system, wherein the alert signal causes the on-board diagnostic system to provide an indication of the condition of the exhaust treatment component to a user.
13. The system of claim 12 , wherein the exhaust treatment component comprises at least one of a hydrocarbon oxidation catalyst and a particulate matter filter.
14. The system of claim 12 , further comprising a NO x sensor positioned downstream of the SCR catalyst and structured to detect a level of NO x in exhaust gas downstream of the SCR catalyst, wherein the normalized level of NO x is equal to the detected level of NO x divided by a ratio of the flow rate of ammonia entering the SCR catalyst to the flow rate of NO x entering the SCR catalyst.
15. The system of claim 12 , wherein the controller determines the normalized level of NO x and the condition of the exhaust treatment components only during transient engine operating conditions and if a temperature condition of the SCR catalyst is within a predetermined temperature range.
16. A method for diagnosing a condition of a component of an exhaust aftertreatment system in exhaust receiving communication with an internal combustion engine, the exhaust aftertreatment system having a selective catalytic reduction (SCR) catalyst downstream of the component, comprising:
detecting a quantity of nitrogen-oxide (NO x ) in exhaust gas downstream of the SCR catalyst;
normalizing the detected quantity of NO x based on a ratio of an ammonia NH 3 flow rate upstream of the SCR catalyst to a NO x flow rate upstream of the SCR catalyst;
determining the condition of the component based on the normalized detected quantity of NO x ; and
communicating an alert signal to an on-board diagnostic system, wherein the alert signal causes the on-board diagnostic system to provide an indication of the condition of the component to a user.
17. The method of claim 16 , wherein detecting the quantity of NO x normalizing the detected quantity of NO x , and determining the condition of the component is performed only during transient operating conditions and when a temperature condition of the SCR catalyst is within a predetermined temperature range.
18. The method of claim 16 , wherein determining the condition of the component comprises comparing the normalized detected quantity of NO x to a predetermined NO x threshold.
19. The method of claim 18 , wherein determining the condition of the component comprises upwardly incrementing a condition metric if the normalized detected quantity of NO x exceeds the predetermined threshold, and downwardly incrementing the condition metric if the normalized detected quantity of NO x is less than the predetermined threshold, and wherein determining the condition of the component further comprises assigning a first condition to the component when the condition metric equals an upper threshold and assigning a second condition to the component when the condition metric equals a lower threshold.
20. The method of claim 16 , wherein providing an indication of the condition of the component includes providing at least one of a visual alert and an auditory alert.